Field of the Invention
The present invention relates to a liquid discharge head and a liquid discharge apparatus that uses the liquid discharge head.
Description of the Related Art
A liquid discharge apparatus that records by discharging liquid onto a recording medium uses a liquid discharge head having a pressure chamber communicating with a discharge orifice and a recording element that provides energy for discharging to liquid within the pressure chamber. In inkjet recording apparatus, which is representative of liquid discharge apparatuses, discharges recording liquid from discharge orifices. The recording liquid is a color material such as dye or pigment contained in a medium. In a case where the liquid to be discharged is a recording liquid in such a liquid discharge apparatus for example, volatile components in the recording liquid near discharge orifices may evaporate, and the concentration of color material increase accordingly, leading to irregular color in the recorded image. There also are cases where the evaporation of the volatile components raises the viscosity of the liquid near the discharge orifices, which reduces the discharge speed of the liquid, and consequently the liquid cannot accurately reach the intended position on the recording medium. Evaporation of volatile components can also cause clogging of the discharge orifices and pressure chambers or the like.
One known measure to handle such an issue is to circulate liquid through the liquid discharge head, and particularly through the pressure chambers. For example, PCT Japanese Translation Patent Publication No. 2003-505281 discloses providing a discharge orifice and recording element for each pressure chamber, providing channels that branch from a common supply channel, pass through the pressure chambers, and merge at a common recovery channel, and to cause a great amount of recording liquid to flow over this channel.
Although the individual pressure chambers in the liquid discharge head 3 and the channels connecting thereto are relatively narrow, the configuration described in PCT Japanese Translation Patent Publication No. 2003-505281 causes a greater amount of liquid to flow through narrow channels than that discharged from the discharge orifices, resulting in increased pressure distribution (pressure drip) within the channels. If the variation in pressure distribution or pressure is great, variation will also occur in discharge properties from the discharge orifices, and quality of the recording formed on the recording medium will deteriorate. It is conceivable to flow the liquid to the pressure chambers at a small flow rate to avoid such deterioration in quality. However, if the amount of liquid circulating through the pressure chambers is reduced, there are cases where high-temperature liquid that has passed through the pressure chambers and flowed downstream will back up toward the pressure chambers if the amount of liquid being discharged from the discharge orifices by driving of the recording elements suddenly increases. This heat of the backflow liquid combined with the heat from driving the recording elements will make the temperature of the liquid near the discharge orifices even hotter. On the other hand, if a state where liquid is discharged from the discharge orifices continues, the liquid which has become hot as described above is gradually discharged, and is replaced by supply of cool liquid into the pressure chambers. As a result, the temperature of the liquid near the discharge orifices gradually returns to normal temperature. Thus, in an arrangement where the flow rate of the liquid circulating through the pressure chambers is small, the temperature of the liquid near the discharge orifices temporarily rises as the recording operations start, and thereafter return to a normal state. This temperature change may change the discharge speed or discharge amount of the liquid, and affect recording quality.